Generally, a wind turbine includes a tower, a nacelle mounted on the tower, and a rotor coupled to the nacelle. The rotor typically includes a rotatable hub and a plurality of rotor blades coupled to and extending outwardly from the hub. Each rotor blade may be spaced about the hub so as to facilitate rotating the rotor to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy.
During operation of a wind turbine, the outer surface of the rotor blades often becomes fouled or roughened over time. For example, dust, pollen, insects, and/or other debris may often collect along the other surface of a rotor blade, particularly adjacent to the leading edge of the rotor blade. In addition, various deposits may often form along the outer surface of a rotor blade, such as salt crystals, ice and/or like, thereby having a roughening effect on the rotor blades. Moreover, surface roughness of the rotor blades may also be caused due to erosion (e.g., sand erosion) and other blade damage (e.g., damage caused by avian impacts), as well as due to manufacturing defects.
When rotor blades become aerodynamically rough due to fouling and/or other factors, the amount of power generated by the wind turbine (and, thus, its Annual Energy Production (AEP)) is decreased significantly. This is mainly due to the reduced blade performance (e.g., reduced lift characteristics, increased drag, earlier stall, etc.) that results when increased surface roughness causes the transition point of laminar flow to turbulent flow across the rotor blade to move upstream towards the leading edge, which further results in increased wall shear and boundary layer thickness. In addition to such reduction in performance, increased surface roughness may also result in a significant increase in the amount of noise generated by the rotor blades.
Accordingly, a system and method for controlling a wind turbine in response to identified blade surface conditions (e.g., increased surface roughness) that allows for a wind turbine's AEP to be increased and/or the amount of noise generated by the rotor blades to be reduced despite the presence of aerodynamically rough blades surfaces would be welcomed in the technology.